PHOENIX -- The man who threw Phoenix Sky Harbor International Airport into a panic Sunday after he abandoned a rental car near Terminal 4 — leading to a nearly-four hour closure, about 300 flight delays and dozens of flight cancellations — will face nothing more than a traffic citation.

But Janet Cappo and her husband, Gerald, didn't know that when they arrived at Phoenix Sky Harbor at about 7:15 a.m. local time — three hours before their American Airlines flight was scheduled to depart for Detroit.

They noticed dozens of police cars packed into Terminal 4 as they passed through on their way to the rental car return.

"We knew something big had to be going on, but we had no ideas what it could have been," she said.

As the couple boarded the shuttle back to the airport, their driver was told not to approach Terminal 4 and to drop them off at Terminal 3 instead.

They figured they would just take the PHX SkyTrain to their actual terminal. They soon discovered the train wasn't moving or letting any passengers board.

The couple patiently waited for the next train.

They didn't yet know that they would spend the next few hours stuck in that same small room with hundreds of others without any information about what was unfoldingoutside at the airport and why they weren't allowed to leave.

It wasn't just a routine towing call

The four-door silver Nissan was idling on the curb line of the upper deck of Terminal 4 for at least 25 minutes before police called it into Alliance Towing, one witness said.

For nearly a decade, Alliance Towing owner Richard Polanco Jr. has been tasked with towing away cars left behind at the airport while loved ones rushed into the airport in search of travelers who left behind an ID, wallet, phone or some other personal belonging.

Polanco figured this towing job would be the same as all of the others.

That changed when he arrived at the airport only to be turned away after police told him they had found a trace of something on the car. Polanco told The Arizona Republic he wasn't sure what exactly police had discovered.

Polanco said officers told him to wait off-site for their call to tow the vehicle.

The Phoenix bomb squad and a bomb-defusing robot spent the next four hours working to determine whether the car was innocently left behind or if it was actually packed with explosives and intentionally planted at the terminal of one of the busiest airports in the nation.

Hundreds wait at Sky Harbor, delays nationwide

Soon hundreds of travelers filled the Terminal 3 SkyTrain platform.

At other airports across the country, passengers traveling to Phoenix were delayed for hours while police searched the abandoned car thousands of miles away.

On Twitter, one woman said she was missing a friend's bridal shower because of a canceled flight.

To the person who left their car curbside at the airport & shut down terminal 4 causing my flight to be cancelled to my best friends bridal shower - hey, its cool. I get it. Ive contimplated that many times. Hope wherever ur headed is worth the trouble ur about to be in tho 😕

Twitter user @ryanhintze called the driver of the abandoned vehicle "selfish."

Hintze wrote in a direct message that as of 3:17 p.m. he was still sitting in his plane at McCarran International Airport in Las Vegas. He was traveling to Tampa, but had a layover in Phoenix.

"An inconsiderate person decided to waste thousands of people's time and inconvenience them," Hintze wrote in a direct message. "I hope the idiot who left the rental car gets tracked down and punished to the fullest extent of the law."

Dian Squire and countless other travelers sat on the floor with their packed bags as they waited for information from the Transportation Security Administration or airport staff.

Squire turned to Twitter in search of any updates after his American Airlines flight to Detroit was delayed multiple times.

Phoenix Sky Harbor International Airport travelers wait for updates Sept. 16, during a closure at Terminal 4 due to police activity.(Photo11: Courtesy of Stephen Griffin)

Airport volunteers brought therapy dogs to help calm the growing crowd while staff passed out water bottles.

Passengers speculated whether they could spot any planes taking off or landing from their distant view of the runway. Others thought they heard loud booming noises from the terminal outside while they checked the status of their own flight on their phones.

"People are surprisingly calm," Squire said in a message to The Republic from inside the terminal. "I think a security threat is more manageable in people’s mind than a plane delay for other reasons. I bet that’s different for people stuck in the terminal itself."

At about 10 a.m., an airline employee climbed onto one of the chairs and shouted to the crowd that all flights had stopped, but they would start again shortly.

Traveler Janet Cappo said he didn't share any additional information.

More and more people packed into the Sky Train station. They had no idea anything was amiss.

Then, with no fanfare, the trains suddenly began running again at about 11:15 a.m.

'An idiotic mistake'

The abandoned car, a silver Nissan, after it was towed from Phoenix Sky Harbor Airport by Alliance Towing, Sept. 16, 2018.(Photo11: Courtesy of Richard Polanco, Jr)

Five hours passed before Polanco got the go-ahead from police to tow the damaged car after investigators determined it wasn't a threat.

The windows of the silver Nissan were shattered and glass shards were scattered on the street alongside Terminal 4. The front hood and trunk was ripped open as the bomb squad searched the car for explosives.

Polanco noticed the driver of the car was still talking to police while he hooked the car up to his tow truck. He offered to give the driver a ride to his tow lot.

The man chatted on his cell phone while he sat in the passenger seat of Polanco's truck. Polanco could hear him telling his family and girlfriend he had been detained and questioned by police for hours.

Polanco said the driver thought only a few minutes had passed after he ran into the terminal to help his girlfriend check into her flight. He didn't know his rental vehicle was already being torn apart by the bomb squad when he returned.

Polanco and the man chatted for a few minutes after he hung up the phone.

"He was just bummed out that for something so small — an idiotic mistake he made — turned into such a big deal," Polanco said.

He never thought to ask for the man's name.

Consequences for the driver?

Phoenix police Sgt. Tommy Thompson said the man likely won't face any repercussions other than a parking citation. He declined to release the man's name because the police department does not publicly identify people who aren't placed under arrest.

Thompson said he was informed that the ticket would likely be about $56. It was not immediately clear whether the driver would have to pay for the damage to the vehicle or the towing fee.

'This whole thing was a mess'

Squire, who was traveling to Detroit, said his flight was pushed to 4:15 p.m. after the airport reopened.

Others, like Florida resident Chris Gaastra, were forced to re-schedule important doctors appointments and other personal, work or family occasions.

Gaastra and her boyfriend stayed in a Phoenix hotel overnight after they missed their flight home. Another flight wasn't available until Monday. It would have cost them thousands of dollars to book an earlier flight with another airline.

"There's nothing I can do about it and I'm just happy that it wasn't a bomb," she said. "Sad the person was that stupid."

Janet Cappo missed her flight to Detroit entirely. Her husband, who was scheduled to fly separately to Los Angeles, was also stranded after his flight was canceled. There weren't any open flights scheduled for the rest of the day.

The couple decided it wasn't worth the wait after they saw the mess of thousands of stranded people.

So they rented a car with plans to make the six-hour drive to Los Angeles. From there, Janet planned to fly home tomorrow night to see her grandchildren.

Lufthansa's newest Boeing 747-8i takes off from Paine Field in Everett, Wash., on its delivery flight to Frankfurt, Germany, on March 25, 2015. The jet is painted in retro colors from the 1970s. Jeremy Dwyer-Lindgren for USA TODAY

Lufthansa's newest Boeing 747-8i takes off from Paine Field in Everett, Wash., on its delivery flight to Frankfurt, Germany, on March 25, 2015. The jet is painted in retro colors from the 1970s. Jeremy Dwyer-Lindgren for USA TODAY